Timers that provide an alert or signal at the expiration of a set time are as old as the hourglass.
Later, mechanical timers typically comprised a spring, a governor or balance wheel, a knob for winding the spring, a pointer, and a dial with markings. The user would turn the knob to both set a desired time and to wind the spring. The timer ran at a (hopefully) fixed speed, calibrated to the dial. When the set time was up, the spring would also power a bell, announcing the completion of the set interval.
Now, electronic timers are prevalent. A common format comprises a keyboard, typically with the digits 0 through 9 plus a few function keys, such as start, pause, and reset. These timers usually include a display, such as an LCD, initially showing the time interval being set, and then the time remaining. An audible alarm announcements completion, often continuous until the alarm is manually cleared.
Such electronic timers are cheaper and more reliable that the mechanical timers they replaced. However, they suffer from many disadvantages. The buttons are usually small—hard to see and hard for many people to operate. Similarly, the displays are often small and hard to see. Such timers are effectively useless in the dark, and hard to use in dim light, or for people who are not wearing their glasses. They are very difficult for people to use who have limited use of their fingers or hands, or have limited eyesight.
In addition, electronic timers are neither fast to set, nor intuitive. While a traditional mechanical timer required no more than a twist of the knob, electronic timers require a specific sequence of buttons to be pushed. Such multiple actions require accurate sight, dexterity and thinking.
In addition, electronic timers, typically, have other disadvantages. For example, they use batteries that must be replaced, they are not waterproof, and they break easily. Although these weaknesses could be overcome by engineering, design and money, the inherent elements of the current art of electronic timers, such as keyboards and displays, make such ruggedization challenging, and, in practice, is not done. Multiple button sequences and the need for light are endemic requirements for current electronic timers.
Devices such as smart phones include timers as applications. Although the user interfaces for these are dramatic improvements over electronic timers, such as the use of voice commands to set the timer, they require an expensive, fragile and theft-prone platform on which to run. They are not suitable for dedicated use, nor appropriate for rugged applications. Such expensive devices are rarely used as kitchen timers because of the dangers in the kitchen of spills and dropping. Voice programmed apps do not respond to all languages, nor to all speakers.
Both electronic timers and smart-phone timing applications may provide illuminated displays. However, the power usage of such displays then requires either frequent battery changes or frequent charging—both of which are a serious inconvenience and often result in a non-operational timer when needed.
In addition, all such timers discussed above rarely permit more than one time interval to be set concurrently. Nor do such timers announce the length of a set time interval at the completion of the interval.